The present invention relates to a semiconductor device, a battery pack, and a mobile terminal.
Among the CPUs (Central Processing Units) in internal circuits installed in mobile terminals, such as laptop computers, there is a type of CPU that has a variable frequency function in order to keep a balance among the power consumption, the calculation performance, and the reliability (life span). The term “variable frequency function” refers to a function in which in the normal operation state, the clock frequency of the CPU is lowered (normal clock operation) to thereby suppress an increase in power consumption, while the CPU is maintained at a low temperature to thereby suppress deterioration in reliability, and when the number of resource requests from the application(s) increases, the clock frequency of the CPU is raised (high-speed clock operation) to thereby improve the calculation performance.
When the CPU is driven by electric power supplied from a battery (an assembled battery in which a plurality of secondary battery cells are combined), the high-speed clock operation period and the clock frequency in the high-speed clock operation state is determined based on the amount of available power of the battery. For example, the CPU is configured to be able to select a plurality of clock frequencies, which are higher than the clock frequency in the normal clock operation state, as the clock frequency in the high-speed clock operation state. Based on the amount of available power of the battery at that time, an optimum clock frequency is selected.
On the other hand, the state of a battery installed in a mobile terminal, such as a laptop computer, is monitored by a battery monitoring system installed in a battery pack together with the battery. The battery monitoring system generally includes a battery control IC (FGIC: Fuel Gauge IC), a sense resistor for detecting charge and discharge currents of the battery as voltage information, a charge control MOS transistor, a discharge control MOS transistor, and a protection circuit such as a thermistor or a fuse. The battery control IC includes, for example, a microcontroller, and implements a function of managing a remaining battery level, a function of controlling charge control/discharge control MOS transistors, a battery protection function, and the like. For example, the battery control IC generates information indicating the state of the battery based on the detection results of the charge and discharge currents and battery voltage of the battery, and notifies the internal circuit in the mobile terminal about the generated information. Examples of the information indicating the state of the battery include a full charge capacity (FCC), a battery remaining capacity (RC), and a state of charge (SOC) of the battery. Japanese Unexamined Patent Application Publication Nos. 2010-34016, 2003-79059, and 2001-51029 disclose related art.
The battery control IC generates not only the information indicating the state of the battery, but also information about a maximum power amount, which is the amount of maximum power that can be supplied to the internal circuit from the battery, based on the measurement results of the discharge current and battery voltage of the battery. A notification regarding the information about the maximum power amount is transmitted, as needed (for example, once per second), to the PC system (internal circuit) of the laptop computer, and is used to determine the high-speed clock operation period and the clock frequency in the high-speed clock operation state.